<March 30, 2008>
Drilled F-717 Longerons to WD-603 Engine Mount Bracket
Oh my! Two weeks have past and I am just updating this page now on April 19th. Wow, I really am slacking!
After seeing where I was in the process, Mike Bullock emailed me the other day to caution me about the edge distance on the bolt holes that penetrate the bottom flange of the WD-603 Lower Engine Mount Bracket. He had some very minor issues with his, and wanted to warn me in advance. Thanks for the heads up Mike!
After thinking about it for a few minutes, I came up with an idea that should allow me to test the edge distance of these holes before I drill the Lowere Longerons. I had about 6" of extra lower longeron angle left over and I decided to make a drilling jig or test piece with it. I measures and marked the locations of the holes per the plans, and drilled the holes to #30 on the drill press. Actually, I dicovered I made a mistake in the spacing of the holes, but it didn't much matter as this was only a test piece and I caught before I drilled the real longerons.
With my longeron test piece drilled, I clamped it to the firewall bracket, and marked the locations of the holes through the angle and onto the bracket with a Sharpie.
The holes would be centered 9/32" from the edge, which is a bit short for the desired edge distance for a AN3 bolt. Based on this I decided I would move the holes inboard another 1/32"-1/16" of an inch. It's not much, but every little bit counts.
With this in mind, I marked the locations for the holes 7/16" from the inboard edge of bottom flange of the longeron rather than the specified 1/2". I them clamped and drilled the longeron with a #30.
I test fit the longeron and marked the locations of the holes. You can see that they ended up just a touch inboard of their original location. The top two holes are now in the correct location, as opposed to the mistake I had made when drilling my test piece.
It was then just a simple matter of clamping and drilling. I started with a #30 and worked my way up to my 3/16" reamer. It all worked great.
Time to drill the other side. Here is how I clamped the longeron to the Engine Mount Bracket. I don't think it is going to move, do you?
That 3/16" reamer sure does a nice job at producing nice round holes. I am really happy with how this went and the edge distance is acceptable (equal with the plans).
Next it was time to fabricate the F-684 Gussets. The hardest part of all these was finding where I had stored them. Seriously, there are a lot of dimensions to mark, cut and drill. I used 1/4" drill bit to drill the holes that will make up the 1/8" radius to the corners of the little cut-out.
Once they were trimmed to the proper dimensions, I clamped them into the vise and bent the flanges using my hand seamer. You are supposed to bend on inboard and one outboard so it took a little bit of thought to make sure I was bending each flange the correct direction.
All done and ready to be drilled to the fuse.
It was getting last and I was tired, but before I headed in for the night I clamped one of the gussets in place to test its fit. Looks good so far, but this is just a rough fit.